D-aspartic acid is an amino acid in the regulation of male sex hormones, such as testosterone. Some research has shown that sodium D-aspartic acid supplements can increase sperm concentration and motility.

An amino acid, L-arginine appears to play several different roles in male fertility. Inside the body, it transforms into nitric oxide, which promotes sperm function.

L-arginine supplements have been found to increase sperm count in rabbits at certain doses. However, the same study found that too high of a dose of L-arginine decreased sperm motility. You should talk to your doctor about how L-arginine may affect you before adding more to your diet.